Means for protecting sheaths of electric cables, pipes, and other metal articles agaist corrosion



June 4, 1940. T. L. osBoRNE Er Al. 2,203,232

MEANS FOR PROTECTING SHEATHS 0F ELECTRIC CABLES, PIPES,

AND OTHER METAL ARTICLES AGAINST CORROSION Filed nay 11, 1938 Fig. 2.

Patented June 4, 1940 MEANS FOR PBOTECTING SHEATHS F ELECTRIC CABLES, PIPES, AND OTHER METAL ARTICLES AGAINST CORROSION Thomas Lloyd Osborne and Harold John Allcock,

Belvedere, Kent, England, assignors -to Callenders Cable and Construction Company Limited, London, England, a. British company Application May 11', 1938, Serial No. 207,301 In Great Britain May 27,1937

4 clam (ci. sai-es) This invention is concerned with the production of wrappings, of impregnated paper and cotton and other textile fabrics formed of natural cellulosic materials, such as are used for 5 protecting sheaths of electric cables, pipes and other metal articles against corrosion and proceeds from the discovery that when natural cellulosic material is subjected to a vacuum and heat in the presence of rosin it undergoes a chemical change on the surface which appears to be an esterification, cellulose rosinate being produced. This reaction, which is accompanied by the production of water that must be removed for the reaction to continue, can be employed, as described and claimed in the specification of copending United States application, Serial No. 207,299 filed on May 11, 1938, for the purpose of making paper 'or fabric resistant to water.

In accordance with the present invention we provide a cable sheath, pipe or other metal body with a protective covering comprising one or more wrappings of a material, consisting of paper or cotton or other fabric formed from -natural cellulosicmaterial, of which, the bres have been coated with a lm of cellulose rosinate by drying the material by subjecting it to heat and a vacuum in the presence of rosin and of which the passages between vthe coated fibres have been sealed by impregnatingthe vacuum dried :materialA with a water excluding compound. The coating of cellulose-rosinate on the 'fibres reduces the water absorptive capacity of the material and to a large' extent overcomes the dimculty experienced with existing coverings formed of paper or fabric impregnated with a water lexcluding compound which merely fills the passages between the fibres, of preventing the passage of moisture through the fabric by way of the bres themselves. In the case of' paper and felted fabric, the cellulose rosinate coating also hasthe advantage of giving it the power to resist the softening and disintegrating action of water.

The accompanying drawing shows by way of example a length of a lead sheathed electric cable furnished with a corrosionvresistant protective covering lconstructed in accordance with the invention. In the drawing Figure l is a perspective view of the protected cable from which portions of the component parts have been removed to expose the construction thereof, and

Figure 2 is a cross-sectional view, on an enlarged scale, of 'the cable shown in Figure l. i

The illustrated cable comprises a stranded conductor I surrounded by a. body of dielectric 2 and a. seamless lead or lead alloy sheath 3. Surrounding the sheath 3 are two mappings i and 5 of cellulosic material, for instance, paper or cotton tape, of which the iibres are coated.Y with a. lm of cellulose rosinate and o which the interstices between the coated fibres are sealed by a. water excluding compound. The wrappings 4 and 5 are so arranged that the small gap between successive turns of the wrapping 4 are bridged by the turns of the wrapping 5. Over the wrapping 5 is a wrapping of fabric material 6, for instance, hessian, on which is arranged a single layer of -wire armouring i in the usual manner.

The rosin required for the formation ci the water resistant lm on thefibres of the material used in the construction of the improved protective covering may in general m appiiei. in any way which brings it into intimate contact with the fibres of the paper or fabric. This of course, sub-ject to the qualification that the method does not involve the use of any material which disadvantageously affects the peper or fabric, either in its structure or in its properties required for its subsequent use. The rosin may, for instance, be applied in solution or in the form oi a suspension. A solution may, instance, be made by the aid of trichlorethyiene, alcohol or other organic solvent for rosin. Satisfactory results are obtained if thesoiuticn strength is such as to leave about 5 parts bf.' Weight of rosin in parts by weight ci paper or fabric. The paper or fabric is soaked in the solution or suspension, for instance, by it through a bath of the solution or suspension, and the solvent or suspension medium may "Je removed by drying in air or under a pressure less than atmospheric pressure. In the case of paper the rosin may be incorporated in the process of manufacturing the paper, for instance, during the beating stage. Convenienth a rosinsized paper containing about 5% by weight ci rosin may be employed.

The rosin-containing material thus promised or obtained is treated in accordance with the invention by heat drying'v it under vacuum until the reaction has been completed or substantially completed. A suitable treatment comprises drying rosin-containing material for a period varying from about 20 to about 50 hours at a temperature of about C. at an absoiute pressin'e which at the end of the process is not greater than 1 mm. of mercury. This treatment also has the advantage that it leaves thapaper er fabric .dry and with little tendency to taire up moisture.

'The treatment can therefore be applied to the paper or fabric while in rolls and need not inimedlately precede the process of impregnating.

with water excluding compound. Theexiloility of the material is not affectedv Toy the treatment. The sealing ci the passages li-etween the coat ed fibres is eected loy impregnating the vacu=Y um dried material with a water excluding cornpound in the usual way. As examples oi water excluding compoundsare mentioned pitch. tar, bitumen and oil compounds. `llnese materials penetrate into the paper or fabric and adhere to the surface thereof.

The improved protective covering has greatly improved resistance to the penetlration` o mois ture and to the softening eiect or any moisture which does penetrate into it. An ,indication of this is provided ley comparing the tensile strength of ordinary paper impregnated with bitumen and then saturated'withwater with a similar grade of paper vacuum dried in the presence of rosin in accordance with the invention and subsequently impregnated with bitumen and then saturated with water. The following figures have been che tained for a particular grade of paper.

Vnat we claim as our invention is:- l.. A corrosion-resistant protective covering for electric cacle sheatlis, pipes, rods and like articles, comprising ,at least one wrapping oi a maA terial, formed :from natural nbrous cellule-sic substance, of which the bres are coated with a water-resistant nlm or cellulose rosinate vformed in situ and of which the passages between the coated @ores are sealed by a water-excluding compound.

. 2. A corrosion-resistant protective covering for electric cable sheaths, pipes, rods and like articies, comprising at least one wrapping of a nia- Vt'erial.formed from natural nbrous celluloslc substance, of which theibres are individually coated with a water=resistant nlm consisting Fof the reaction product of the surface cellulose of the fibers and rosin and of which the passages loe= tween the coated nbres are Isealed by a watereixcluding compound.

3. A corrosion-resistant protective covering for electric cable sheaths, pipes, rods and like articles, comprising at least one wrapping of a material, formed from natural brous cellulosic sulostance, of which the libres are individually coated with a water-resistant film consisting ol the reaction product of the surface cellulose ot tine irllires and rosin and of which the passages between the coated lores are sealed by bituminous compound. l

4. A corrosion-resisting protective covering :for electric cable sheatns, pipes, rods, and like articles, cornprisine.r at least one wrapping oi' a material formed Afrom natural fibrous cellulosic substances, of which the lores have been superficially esteriled by treatment with rosin, and of which the passages between the supercially esterileol fibres ere sealed by a water-excluding compound.

THUMAS ELOYD @SE-ORNE HARULD mitm ALLCOCK. 

